design of district cooling distribution system for higher availability, reliability, maintainability...
TRANSCRIPT
Muhammad Ali
Design of District Cooling Distribution System for higher
Availability, Reliability, Maintainability and Capability
Contents
1. The Components of Effectiveness2. Availability3. Reliability4. Maintainability5. Capability
A,R,M, and C
Maintainability
Capability
Availability
Reliability
Effectiveness
Effectiveness = Availability * Reliability * Maintainability * Capability
Raw Data from Operating LogsWall Clock Hours
Start End Elapsed Time for Up Time
Elapsed Time for Down Time
0 708.2 708.2 708.2 711.7 3.5711.7 754.1 42.4 754.1 754.7 0.6754.7 1867.5 1112.8
1867.5 1887.4 19.91887.4 2336.8 449.4 2336.8 2348.9 12.12348.9 4447.2 2098.3 4447.2 4452 4.84452 4559.6 107.6
4559.6 4561.1 1.54561.1 5443.9 882.8 5443.9 5450.1 6.25450.1 5629.4 179.3 5629.4 5658.1 28.75658.1 7108.7 1450.6 7108.7 7116.5 7.87116.5 7375.2 258.7 7375.2 7384.9 9.77384.9 7952.3 567.4 7952.3 7967.5 15.27967.5 8315.3 347.8 8315.3 8317.8 2.5
Total 8205.3 112.5MTBM 683.8 MTTR 9.4
MTBM = mean uptime; this is the time between two maintenance periods
MTTR= mean downtime due to maintenance; this is the time when system is down for repair
• Deals with the duration of up-time for operations and is a measure of how often the system is alive and well.
Availability
Up-time ≡ not downtimeA = A hardware*A software*A humans*A interfaces*A process
Availability
98% availability for a continuous process says to expect • up-time of 0.98 * 8760 hours = 8584.8 hrs/year
• down time of 0.02 * 8760 = 175.2 hrs/year, as
Availability + unavailability = 1
Availability
• Design looped network
Availability
LOOP
• Design looped network
Availability
DN 1200
DN 800
DN 1
200
LOOP
• Multiple Supply/Return at Plant
Availability
PLANT-1
PLANT-2
12
1 2
• When high availability is of special importance, install standby “duty assist” pumps. Higher availability might be requested for commercial use than for residential buildings.
• One control valve for each PHE• Multiple heat exchangers
Availability
• Deals with reducing the frequency of failures over a time interval and is a measure of the probability of failure-free operation during a given
interval, i.e., it is a measure of success for a failure free operation
Reliability
R(t)
(Mean Time Between Failures) is the time between system failuresR = R utilities*R feed-plant*R processing*R packaging*R shipping
• For a given mission time, to achieve high reliability, a long MTBF is required.
Reliability
• MTBF = 638.8 hours• Mission time = 1 year = 8760 hoursReliability = R(t)
• MTBF = 30 years• Mission time = 1 year Reliability = R(t)
1
2
=12.8
Reliability
DCP Wadi
DCP West
DCP North
DCP Marina
Cooling plant
• Four main plants : Total Market > 500,000 TR
Reliability
Multiple production sites around the city connected to DC grid
Reliability
• Pre-insulated • Welded end • Direct buried
Eliminating flanges – a potential source of leaks
Reliability
• Deals with duration of maintenance outages or how long it takes to achieve the maintenance actions compared to a datum.
M(t)
MTTR is Mean Time To RepairMaintainability issue is to achieve short repair times for keeping availability high
Maintainability
• Maximum Repair Time 24 hrs
• Maintenance Goal 99.9%
0 5 10 15 200%
10%20%30%40%50%60%70%80%90%
100%
1 25%2 44%3 58%4 68%5 76%6 82%7 87%
8 90%9 92%
10 94%11 96%12 97%
13 98%14 98%15 99%16 99%17 99%18 99%19 100%20 100%21 100%22 100%23 100%
24 100%
Hours
Prob
abili
ty
MTTR 3.48 Hours
Maintainability
• MTTR = mean down time due to maintenance = 9.4 hours
• System Maintainability= ?
If allowed Maximum Repair Time is 10 hoursM(t) = 65.5%
Probability of maintaining the system in allowed time of 10 hours is 65.5%
Maintainability
Maintainability
Minimize need for maintenance; manufacture utilizing high quality material and components
• Install leak detection system• Secure Joints: Do not let water/moisture enter
the HDPE Jacket• Design pipe, works and components for high
life-time; 40 years• 10 years warranty
Maintainability Be Careful with Bends, Fittings and
Valves
MaintainabilityCondensation
problems: LDS to monitor, detect and
locate faults
Building entry sealin concrete walls
and floors
• Deals with productive output compared to inherent productive output which is a measure of how well the production activity is performed compared to the datum.
Capability = Efficiency * Utilization
Efficiency = Productive Work output/ work inputUtilization = Time spent on productive efforts / total time consumed
Capability
• For example; System efficiency 80%Utilization 82.19% (300/365 days)
Capability = 0.8 * 0.8219 = 65.75%
Capability
Remember A,R,M, and C
Maintainability
Capability
Availability
Reliability
Effectiveness
Effectiveness = Availability * Reliability * Maintainability * Capability
